Siemens communication/data transfer question

I have a CPU315-2 PN/DP and a CP 343-1 module on seperate ProfiNet networks, but in the same rack. The CPU network is the device network, and the CP 343 is the plant network. I can get my ProfiNet devices to work on the Device network but not on the Plant network. I also noticed that HW Config is allowing I address and Q addresses to be assigned the same from Device network to Plant network. Even when I make sure the addresses are different I can't get any information to or from the Plant side devices.
I'm finding some stuff out there saying I need to use FC11/FC12 PNIO_SEND and PNIO_RECV, but why would I need to use those if the CP 343 has I and Q addresses in the HW Config?

hi!

The FC11 and FC12 are used to send and receive the signals to and from the CPU and the CP. So it is not considered to be the same, how do you call it, image?

Start your addresses on the CP from 0 and up. And only send as many signals as you declared there.

And yes, it does not make much sense, my first profinet/bus project had me scratching my head for a long time.

Thanks. I managed to finally get the data to come across on the second network. What I wasn't realizing was that the two devices CPU and CP have separate image process areas and that you have to use FC11 and FC12 to get data in between those areas.